JPS622617B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid metal refining apparatus, particularly a liquid metal refining apparatus used in a fast breeder reactor.

Cold traps are installed in the primary and secondary purification systems of a liquid metal cooled fast breeder reactor (hereinafter referred to as a fast reactor) to capture impurities in the liquid metal and purify the liquid metal. ing. FIG. 1 shows the structure of a conventionally used cold trap. This cold trap has a container 1, an inner pipe 2, and a cooling pipe 3 as its main components. A liquid metal outflow pipe 5 is provided at the top with an open bottom end, and a filling layer 6 filled with mesh and an upper plenum 7 are provided inside the pipe, and the bottom of the container 1 and the liquid metal outflow pipe 5 are provided. The lower part of the open end of the inner tube 2 constitutes a settling chamber 8 in which the flow of liquid metal is reversed. The cooling pipe 3 is configured to cover the outside and bottom of the container 1, and a cooling body inlet pipe 9 is provided at the bottom.

In a cold trap having such a structure, liquid metal containing impurities enters the container 1 from the liquid metal inlet pipe 4, flows through the annular gap 10, and then enters the settling chamber 8. While descending, it is cooled by the cooling body flowing through the cooling pipe 3. Since the temperature of the liquid metal decreases during this cooling process, impurities in the liquid metal precipitate at a supersaturated concentration. The flow path of the liquid metal entering the settling chamber 8 is reversed here from downward to upward, so precipitated impurity particles with a large mass settle to the bottom of the settling chamber 8, and some of the impurities in the liquid metal is collected. Other impurities that did not precipitate in the settling chamber 8, together with the liquid metal,
Flow upward from the settling chamber 8 into the packed bed 6
flow inside. In the region of the packed bed 6, some of the impurity particles that have passed through the settling chamber 8 are filtered by the filter effect of the mesh, and the other part is deposited on the mesh surface to remove impurities in the liquid metal. . The liquid metal thus purified enters the upper plenum 7 and the liquid metal outlet pipe 5
out of the cold trap.

Therefore, when purifying liquid metal using such a cold trap, impurities accumulate in the packed bed 6 and the flow path of the liquid metal becomes clogged, as the fast reactor operates. If such flow path blockage occurs, it is necessary to replace the cold trap with a new one. However, due to economic considerations, cold traps are recycled and reused. To regenerate a cold trap, you need 400 cold traps.
The method used is to raise the temperature to ~600°C, redissolve the impurities captured in the mesh and the impurities deposited on the mesh surface in the liquid metal, and drain them outside the cold trap. However, the structural materials and mesh of cold traps exposed to high temperatures and high impurity, especially oxygen, environments accelerate corrosion.
Reuse becomes impossible. Therefore, the cold trap had to be large enough to prevent impurities from clogging the liquid metal flow path until the time of maintenance and inspection of the fast reactor.

The present invention aims to eliminate these problems and provide a liquid metal refining device that can be easily regenerated even if the liquid metal flow path is blocked. , an inner container which is arranged at a certain gap from the inner side of the outer container, has an open bottom end and a liquid metal outlet at the top, and holds a filler for removing impurities in the liquid metal inside. ,
In a liquid metal refining apparatus having a cooling means provided in an outer container, the filler is made of hollow steel balls having the same specific gravity as the liquid metal, and a magnetic field generator is provided to stir the steel balls. This is a characteristic feature.

The function of the cold trap is to refine the concentration of impurities contained in the liquid metal to a target concentration, and its impurity capture ability is determined by the cooling temperature of the liquid metal and the surface area of the filler. The present invention has a structure that is compact and can be easily regenerated even when the flow path is blocked, without impairing this function and ability.

Examples will be described below.

FIG. 2 shows the structure of one embodiment.
The same parts as in the figures are given the same reference numerals, and the difference between this embodiment and the apparatus shown in FIG. 1 is that hollow steel balls 11 are filled inside the inner tube 2, and a drain pipe 13 having a drain valve 12 at
is provided, and a magnetic field generator 14 is attached to the body of the cooling pipe 3.

Then, inside the inner tube 2, a hollow steel ball 1
A grid 15 is provided between the upper plenum 7 and the filling layer 6 formed by filling the upper plenum 7 and at the boundary with the settling chamber 8.

The steel balls 11 filled inside the inner tube 2 have a specific weight depending on the temperature of the ratio t/r of the radius r and the thickness t of the steel ball, and a liquid, where the radius is r and the thickness of the steel ball is t. A steel ball floats or sinks in liquid metal due to the relationship between the specific weight and the temperature of the metal. Figure 3 shows the floating and sinking areas of the steel ball 11 in the liquid metal. The ratio (t/
r) is set, area A indicates the area where the steel ball 11 sinks, area B indicates the area where the steel ball 11 floats,
It is desirable to use a steel ball 11 that is placed on the boundary line C between the sinking region A and the floating region B.

In a cold trap having such a structure, liquid metal containing impurities enters the container 1 from the liquid metal inlet pipe 4, flows through the annular gap 10, and then enters the settling chamber 8. While descending, the impurities in the metal are cooled by the cooling body flowing through the cooling pipe 3, and in this cooling process, the temperature of the liquid metal decreases, so that the impurities in the liquid metal precipitate in their supersaturated concentration. The same is true for conventional devices.

Other impurities that are not precipitated in the settling chamber 8 flow into the packed bed 6 of the steel balls 11 in the apparatus of this embodiment. In the packed bed 6 of the steel balls 11, impurities in the liquid metal are removed by filtration due to a filter effect and by precipitation of impurities on the surface of the steel balls 11. The liquid metal thus purified flows out of the cold trap through the upper plenum 7 and the liquid metal outlet pipe 5.

FIG. 4 shows the cold trap of this embodiment installed in a fast reactor, and the same parts as in FIG. 2 are given the same reference numerals. 16 is a main pipe, 17 is a drain tank, the main pipe 16 and the cold trap container 1 are connected by a liquid metal inflow pipe 4, and the liquid metal inflow pipe 4 is provided with a pressure gauge 18 and a gate valve 19. A pressure gauge 20 and a gate valve 21 are provided in a liquid metal outflow pipe 5 for returning purified liquid metal from the cold trap container 1 into the system.

The drain tank 17 is connected to the cold trap vessel 1 by a drain pipe 13.

When liquid metal is purified using this cold trap, impurities are accumulated in the packed bed 6 of the steel balls 11 as well as the operation results of the fast reactor as described above.
Flow path blockage occurs, but in this situation,
A pressure difference is generated between the pressure gauges 18 and 20 attached to the liquid metal inflow pipe 4 and the liquid metal outflow pipe 5. When this reaches a predetermined differential pressure, the gate valves 19, 2
1 is closed and a voltage is applied to the magnetic field generator 14 to generate a magnetic field, the liquid metal in the cold trap and the steel balls 11 can be stirred. By this stirring, the impurities present between the steel balls and the impurities deposited on the surface of the steel balls are removed by the filtering action and become mixed in the liquid metal. In this state, the drain valve 12 is opened and the liquid metal in the cold trap is drained into the drain tank 17. After draining is completed, the drain valve 12 is closed, and the gate valve 1
9 and 21, and refining the liquid metal in the main pipe 16 is resumed.

In the cold trap of this embodiment, the packed bed 6 of the cold trap is filled with steel balls having the same specific gravity as the liquid metal, so it is easy to stir the liquid metal when the flow path is blocked, and it can be regenerated at the operating temperature. processing becomes possible, and the device can be made more compact. Furthermore, since only mechanical operations are used, the regeneration processing operation is easy and can be applied to computational control.

As described above, the present invention makes it possible to provide a compact liquid metal refining device that can be easily regenerated even if the liquid metal flow path is blocked, and has great industrial effects.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of a conventional liquid metal refining device, FIG. 2 is a vertical sectional view of an embodiment of the liquid metal refining device of the present invention, and FIG. 3 is a diagram showing the relationship between the radius and thickness of a steel ball. Diagram showing the relationship between the ratio and the liquid metal temperature, 4th
The figure is an explanatory diagram showing the state of use of the liquid metal refining apparatus of FIG. 2. DESCRIPTION OF SYMBOLS 1... Container, 2... Inner tube, 3... Liquid metal cooling pipe, 4... Liquid metal inflow pipe, 5... Liquid metal outflow pipe, 6... Filled bed, 7... Upper plenum, 8...
Settling chamber, 9...Cooling body inflow pipe, 10
... Annular gap, 11 ... Steel ball, 12 ... Drain valve, 13 ... Drain pipe, 14 ... Magnetic field generator, 1
5... Grating, 16... Main piping, 17... Drain tank, 18, 20... Pressure gauge, 19, 21... Gate valve.

Claims (1)

[Claims] 1. An outer container having a liquid metal inlet at the top, which is disposed at a certain gap from the inner side of the outer container, has an open bottom end and a liquid metal outlet at the top, and has a container for removing impurities in the liquid metal. A liquid metal refining device having an inner container holding a filler for use in the liquid metal, and a cooling means provided in the outer container, wherein the filler is made of hollow steel balls having the same specific gravity as the liquid metal. A liquid metal refining apparatus characterized in that a magnetic field generator for stirring the steel balls is provided.